A new way to produce conformal cooling channels by RPT for moulding blocks of the hybrid moulds

Prémio de melhor artigo com interesse para a indústria.Hybrid moulds are an increasingly considered alternative for prototype series or short production runs. In this solution of injection moulds the moulding elements (blocks or other inserts) are manufactured in alternative metallic materials or in synthetic materials. One of the main issues associated to the use of these alternative materials is their thermal behaviour. For instance, in order to allow uniformity in the cooling of the moulded part, and a significant cooling time reduction, conformal channels are recommended as an efficient solution. The layout of the channels should contour the geometry of the impression, and has to be easily implemented during the production of the moulding blocks. This paper reports on a case study involving the use of conformal cooling channels obtained in wax by 3D-impression. An injection hybrid mould of a simple geometry production was used for testing several possibilities of conformal cooling construction. The discussion of cure parameters of the epoxy-based composite resin that can have influence on the wax thermal properties is presented alongside with recommendations for the use of this rapid tooling technique

Rediscovering structural foams in injection moulding

EU program QREN contract 2010/013307 - project 'Hybridmould 21'Strategic Project PEst-C/CTM/LA0025/201

Prediction of stiffness from orientation data of glass reinforced injection moldings

The complex thermo-mechanical process developing in injection molding leads to through-thickness and point to point variation of fiber orientation. It is not economically viable to characterize experimentally the variation of fiber orientation. Thus, efforts have been put into modeling the fiber orientation in injection molding. Some commercially available programs already allow the prediction of fiber orientation distribution in moldings. If the fiber orientation field is known it is possible to calculate the major elastic properties, which can be input into finite-element structural analysis codes to predict product performance. That approach was followed in this work to compare the experimental flexure behavior of glass fiber reinforced polycarbonate injection molded discs with predictions obtained from FEM simulations. The data used in the FEM code was calculated from the fiber orientation data predicted using the software C-Mold.(undefined

Is there any chance for polypropylene/clay nanocomposites in injection molding?

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Study of the processing and properties of mixtures of recycled plastics for outdoor applications

There is an industrial need for the study of the mechanical and physical properties of recycled polyolefins mixed with cellulose fibres from diapers, wood and packaging containing aluminium. The recycling of thermoplastic based residues is economically very interesting for the easy reprocessing of these materials and flexible shaping using conventional moulding processes as injection moulding or intrusion. Various mixtures of these materials were characterized in terms of their constituents and properties determined using 200 mm square mouldings of 10 mm and 5 mm thickness, in view of their potential application in urban furniture. These mouldings were processed by injection moulding and by intrusion that is a method which uses and extruder for delivering the melt directly into an injection mould. The mouldings were tested in terms of theirmechanical performance in impact and flexion. The intrusion process yielded mouldings with properties similar to injection moulding but appeared to be more attractive for requiring lower moulding pressure and thus lighter and cheaper tooling. The morphology of the mouldings, observed by bright field light microscopy showed some contamination and voiding associated to specific processing conditions and moulding size, the thinner mouldings having less voids than the 10 mm thick. The higher voiding in the thicker mouldings was detrimental to the flexural and impact performances of the parts. The coefficient of linear thermal expansion was determined and showed to be sensitive to the percentage of LDPE and fibres in the mixtures. The flexural stiffness of the moulded plates was assessed using the whole mouldings in the 3-point support test and showed the positive influence of the wood fibres and the diaper content in the mixtures. Conversely the impact performance assessed by the Charpy test was affected by the diaper content, but benefitted from the presence of aluminium from the recycled packaging. The prediction of these properties using the law of mixtures for predicting the overall density in the mouldings was not particularly accurate for the mixtures with recycled diapers.European Commission for Education and Training, Erasmus placement scholarship at Hogeschool Gen

Effect of melt viscosity on the ejection force in injection moulds

This paper shows data on the ejection force of injection mouldings. The tubular mouldings are pin gated. Two polypropylenes with different melt viscosities (melt flow indices) were investigated. Experimental focus is put on the effect of the holding pressure, mould temperature and the cooling time on the measured ejection force. Pressure and temperature were continuously monitored with transducers during the filling process. The ejection force was directly measured with load cells. The results show that higher viscosity lends to higher ejection force.(undefined

The effect of holding pressure on the shrinkage and birefringence of injection moulded polypropylene plates

This paper shows the results of shrinkage and birefringence of injection moulded plates. The study was done with two polypropylenes with different MFI. Focus is made on the effect of the holding pressure on the experimental as-moulded shrinkage and birefringence in the flow direction. The mouldings are edge gated flat rectangular plate. The moulding process was continuously monitored with pressure transducers. The results show that the rise of holding pressure determines the decrease of the shrinkage. Also, it was observed that the increase of the pressure applied during the holding phase and the associated flow induce re-orientation of the melt, especially in the case of higher molecular weight PP. Consequently, an increase in the birefringence results.(undefined

Test equipment

During the ejection phase of the injection moulding cycle the parts are mechanically forced to separate from the moulding surfaces, this aspect being more relevant with deep cores. The design of the ejection system depends on factors such as the draft angles, the surface finish, and the properties of the moulding material at the ejection temperature and the dimensioning of actuation devices (e.g., hydraulic or pneumatic cylinders). Knowledge of the friction properties of the mating metal and plastics surfaces is important to optimize the ejection system. The coefficient of friction at the ejection stage depends on the surface texture of the core and the temperature at ejection. This paper reviews recent research on the static coefficient of friction in moulding conditions. It also reviews results obtained with a prototype apparatus that reproduces the conditions occurring during the ejection phase.Portuguese Foundation for Science and Technology (Research Grant POCTI/ 32978/CTM/2000—Project Mouldfriction)Agency for Innovation (Research Grant IC-PMEP0015— Project Mouldforce

Experimental validation of morphology simulation in glass fibre reinforced polycarbonate discs

As assessment is made between Moldflow simulations and experimentally determined fibre orientation distributions at three points along the flow path and 12 layers across the thickness. The material used is a 10% weight short glass fibre reinforced polycarbonate. With this material the physical interaction between fibres during flow is minimised. Centre gated circular discs, where both the shear and the extensional flows are present, were produced over a range of moulding conditions to analyse the effect of flow rate and melt temperature upon the fibre orientation. The fibre orientation was measured using image analysis tools in images obtained by reflection microscopy of polished sections, using the method proposed by Bay. The measurements were made in 12 layers across the thickness